Motion transmitting linkwork



Feb. 6, 1945. P. F. EvERrr'r MOTION TRANSMITTING LINKWORK QFiled Aug.13, 1943 Patented Feb. 6, 1945 lassegna Morton' TRANsNnT'rING-LINKWORKvPhilip-frrancist Everitt, nforegnngimdaassigner ottone-.half to HenryHug-hes 8a/SonN Limited London', England,l a; British. limited-hability.

Application'. August313, 1943, Serial No: 498:,5163 In Great BritainAugust 171; 1942;

6' Claims.

This-invention relates to improvements in motion-'transmitting linkworkandi has particular reference totl'iev parallelfmotion'linkworkcoupling' a chart rule with theI `main actuating spindle of'trigonometrical' computing: devices suchas apparatus for solvingtriangle-s. Y

The object of the invention is to provide relatively simple, robustandinexpensive mechanism try-which the computing device, which ismountedon` a. 'fixed chart, can, inieii'ect,be turned' relatively' tov thechart Withoutdisturbing the physicalrelationship. i v l iThe'inventionfurther providesv meansby which the' positive vrelation`oil the edge of thei chart-rule caneasily be adjusted relativelyv tothe `datum linezof the computing device- In ordinary draftingmachines-thev rulergis mounted on a'. freefterminal thatis'connecte'd"to a junction element by twolequiangul'arly related similar parallelmotions; eachI of which isa closed kinematicA four link chain withparallelcranks ofthe same length and thejunction element' in turn isconnected to` a stationary bracket (mounted on theV drawing board) byItwo equiangularly relatedsimilar parallel motions each of whichA also isa closedl kinematic four 'link chain Witlfiv parallel! cranks of i the.same length;

Such *an* arrangement` on. they one. hand; allows the ruler to be movedover'.the' drawingboard without undesirable constraint onlthe otherlianclg. operates rigidly` t maintain:k the: edgefof the; ruler parallelwith'a givenline. regardless-Pof thev linear displacements of'.saidiruler upf vand down or to. and fro.- on thefdrawingboard but-isquite unsuited to transmit'continuoustrotation of a: freeV terminal to.and from a; junction element owing.: to: the` ambiguous conditions thatoccur lin thee linkwork'. at. points; in. the rotation separated bylthepivot-'pitch' when it is. approximately 1-80 angular degrees. y

Toi transmit. the rotation of a free terminal to and from a 4junctionelement smoothly' andffcontinuously; at; least;4 three kinematicchainsof' the kindf referred to'fsuperimposed' in" angular rela-vtionmustbe usedf. v

The invention consists in improved motion transmittinglinkworkfcliaracterized in that the rotation of a free terminal isaccurately trans-l mitted to a junction element and from said junctionelement to a spindle by sets of'three or more parallel motions.

Generally, the improved motion transmitting linkwork permits ofunconstrained linear displacement of a terminal over a limited chartsurface and .transmits any rotary movementof said i y the. surfacezzc:of. the yclfarti (imFigurel repieterminal* accurately to` af junctionelem-ent: and

from tliefjunction'elementto a spindle. 'To this end the freefterminalAis connectedfto'the junction element" by4 three or more angularlyrelated similarl parallel 'motion transmitting means each of l whichforms'a;4 closed kinematic fioul-"link chain with-'parallel cranks'foftllesame length. The

junction elementsimilarlyVA is .connected to. said spindle bythreeNor'rmoreqangularlyrelated'similarparazllelf motions, each -ofwhich.` is .av 'closed -ltlnematic'- four'v4 'link'ichain .witltparallel :cranks oil the same: length-sodthat when saidl improvedlmkwnpk .isz-applied vto ya1.trigonometricall comput-v ing device ot'thee kindfrei'erredi to.. `the* angular relationship' of` thefdevice to:`the vchart ican,.f1in

client, beiclfianged by rotating: the chartrulawith-,

relationshipof .the

being'V had to the figures tnereo inf Whiclisimilar letters refer tosimilar parts and in which:v

lFigurew L is: a; Idiagranmrati'c'plan` view of;v` theimprovedllinltworkgand Figure/221s; aasid'e'v elevation; of. Figure 1.looking l -in the.l` direction oft the arrowN 2;infthat.figure.H

. Inaltlre: arrangement*` showniniy the' drawing, x a

is the main actuating spindle offthetrigonometril-y cali computingdevice. which is oil fixed location p andi lz?V is the chart. rule whichcan` be moved: over sentedfbirthe suriaceeotltliepaper); i.'ll'liefrulez'bsisl mounted onvthe: freer terminali or carrier @whichiis in: theE form-cfa .disc/ somewhat i i mounted" on the similar' totthe disc*- or ffi'angei eg spindle'f.V

"The carrier d1 andi the' ilan'ge er each-'has one end? of eaclif sixflinkspivotallyf mounted there-- j on, that is to say, one end f ofeach-ot the: three `linksgfisiconnected tothe-carrier d' by'afpivot h` yandi one ifotieacli of the' threelinks; kfisc'on: nectedfto theflange-e'byiafpivot' L, thefthree pivetsifmfandl (in effect forming sets ofcranks) beingfequiangularly' spaced. and located-2 atyan equal'distanceV from thefcentersforotationiof i d and. e, respectively. l y

The other ends of the links g and 7c are connected to a. junctionelement m by pivots n `and o respectively which are equiangularly spacedand located at a distance from the centre of the e1ement m equal to thedistances of the pivots'h and `l from the centres of rotation of thecarrier d andA 1 `sets of flange e, thus forming two associated cranks.

i", if a In the drawing, the length of the links y is equal to that ofthe links lc and for purposes of construction, the pivots h are on theupper side of the carrier d, relatively to the surface c ofthe chart,whilst the pivots Z are on the underside of Athe ange e, the pivots nbeing arranged on the under surface of the element m,` whilst the pivotsov are arranged on the upper surface thereof.

Such an arrangement complies with all theV geometricalrequirements andwhilst allowing of unrestrained linear displacement of the'centre of thecarrier d within the limited area ofthe surface c of the chart by virtuel'of the parallel mo` tions, also enables rotation of v,the carrier daboutA its centre to be faithfully transmitted to thespindle a by virtueof the two sets of three angu` larly related closed kinematic chains.

To simplify the description as much as possible' the radial distancesoffall the pivots h, l, n and o' have been referred to as being similar,but ob` viously if the radial distances of the pivots h are the same asthe radial distances of the pivots n and the radial distances ofk thepivots Z are the same as the radial distances of the pivots 0 it isimmaterial whether the radial distances ofthe pivots n are equal `totheradial distances of the pivotsnoor not, they may be greater or lessto suit any constructional requirements.

` Further, the numberof angularly relatedclosed kinematic chainsincluded in a set need not be limited to three, whichis the minimumpossible,` nor need the number of chains inrone set be equal to thenumber of chains in the other set provided that three or more are usedin each set. y

Further, although in the example described closedA kinematic chains ineach set are shown and described as equiangularly related to oneanother, provided that the cranks of one group, say

those onv the carrier d, are similarly related angularly to the cranks`of the associatedY group on the junction element m it is immaterialwhether Y the angles between the cranks are the same or not. 1 A Inorder that the scope and freedom of operation shall be unrestricted,other than by dimensional limitations, the ends of the links g and lcarek offset, as shown in lFigure 2 for example, to-

avoid any fouling'during movement over the surface c of the chart. v

As in some cases it `is necessary or convenient to adjustthe edge of thechart rule b relatively .rotatably mounted spindle ,having angularlyytoV the datum line of lthe computingA device of which a is the spindle,the rule'b is pivoted on the carrier d, usually at the geometricalvcentre p ofthefthree pivots h, so that Aitycan'be turned withoutrotating the spindle a, frictional or other -gripping means beingprovided by which the rule b is retained in adjusted position withsuicient ksecurity to transmit rotatory movements during ordinary use. l

As shown in the drawing the junctionelement m is supported through thelinks y and k but in practice a carriage, that glides with a minimumoffrictionon the surfacec,A isl provided, said carriage co-operatingwith the edge of saidelement by means of roller, ball-or similarantifriction bearings'. f

I claim:

1. A motion transmitting device comprising av and at least threeparallel means rotatably conl nected to said junction yelement and saidspindle at angularly related points whereby rotation of *said terminalelement 'causes equal rotation of said spindle.

2, A motion transmitting linkwork comprising a rotatably mountedspindle, a junction member,

at least three links each having one end con- `nected rotatably to saidspindle at angularly related points spaced equally from the axis of saidspindle, means rotatably connecting the links in parallel relationshipto said junction member at points equidistant from the points ofconnection with said spindle, a terminal member, at least threeVadditional links connected rotatably and in parallel relationship tosaid junction member and said terminal element, the lengths of theadditionall links between the points of connection being equal and thepoints of connection being spaced angularly and equidistant from pointson` said junction member and on said terminal element.

3. A motion transmitting linkwork comprising a spindle, ajunctionelement,A a terminal, each having a center of rotation, at leastthree parallel links having opposite vends connected rotatably to saidspindle and said junction element at angularly related points spacedequidistant from their ,centers of rotation, and at least threeadditional parallel links having opposite'ends connected rotatably tovsaid junction and said terminal elements at angularly related pointsspaced equi-AM distant from their centers of rotation.

4. The motio-n transmitting linkwork set forth in claim 3 in which theterminal element is provided with a chart rule andthe spindle is con-Vnected to a computing device.`

5. The motion transmitting linkworkset forth inclaimgS in which theendsof said links are offset and said additional links are connected tothe one side ofsaid junction element andv the other links are connectedto an opposite side of said junction element.

6. A motion transmitting device comprising a spaced crank meansthereonra terminal member having angularly spaced crank'means thereon, ajunctio-nelementhaving crank means thereon `spaced angularly.r equallyto the spacing of the crank means on said spindle and said terminalmember, at least three `links connecting the crank means' on saidspindle and saidjunction e1ement,'and at least three links connectingthe crank means on said junction element Vand on said terminal member,Asaid connected Vcrank means being `of such length that upon rotation ofsaid'terminal element, the links connected thereto have parallelmotion'sto rotate said junction element and the links connected to saidspindle have parallel motions to rotate said spindle.

. PHILIP FRANCIS EVERITT.

